import sys
import time
import warnings
from pathlib import Path
from typing import Optional

import lightning as L
import torch

from generate import generate
from lit_llama import Tokenizer, LLaMA
from lit_llama.lora import lora
from lit_llama.utils import EmptyInitOnDevice, lazy_load, llama_model_lookup
from scripts.prepare_alpaca import generate_prompt

lora_r = 8
lora_alpha = 16
lora_dropout = 0.05


def main(
    prompt: str = "What food do lamas eat?",
    input: str = "",
    lora_path: Optional[Path] = None,
    pretrained_path: Optional[Path] = None,
    tokenizer_path: Optional[Path] = None,
    quantize: Optional[str] = None,
    dtype: str = "float32",
    max_new_tokens: int = 100,
    top_k: int = 200,
    temperature: float = 0.8,
) -> None:
    """Generates a response based on a given instruction and an optional input.
    This script will only work with checkpoints from the instruction-tuned LoRA model.
    See `finetune_lora.py`.

    Args:
        prompt: The prompt/instruction (Alpaca style).
        lora_path: Path to the checkpoint with trained LoRA weights, which are the output of
            `finetune_lora.py`.
        input: Optional input (Alpaca style).
        pretrained_path: The path to the checkpoint with pretrained LLaMA weights.
        tokenizer_path: The tokenizer path to load.
        quantize: Whether to quantize the model and using which method:
            ``"llm.int8"``: LLM.int8() mode,
            ``"gptq.int4"``: GPTQ 4-bit mode.
        dtype: The dtype to use during generation.
        max_new_tokens: The number of generation steps to take.
        top_k: The number of top most probable tokens to consider in the sampling process.
        temperature: A value controlling the randomness of the sampling process. Higher values result in more random
            samples.
    """
    if not lora_path:
        lora_path = Path("out/lora/alpaca/lit-llama-lora-finetuned.pth")
    if not pretrained_path:
        pretrained_path = Path(f"./checkpoints/lit-llama/7B/lit-llama.pth")
    if not tokenizer_path:
        tokenizer_path = Path("./checkpoints/lit-llama/tokenizer.model")
    
    assert lora_path.is_file()
    assert pretrained_path.is_file()
    assert tokenizer_path.is_file()

    if quantize is not None:
        raise NotImplementedError("Quantization in LoRA is not supported yet")

    fabric = L.Fabric(devices=1)

    dt = getattr(torch, dtype, None)
    if not isinstance(dt, torch.dtype):
        raise ValueError(f"{dtype} is not a valid dtype.")
    dtype = dt

    print("Loading model ...", file=sys.stderr)
    t0 = time.time()

    with (lazy_load(pretrained_path) as pretrained_checkpoint,
          lazy_load(lora_path) as adapter_checkpoint):
        name = llama_model_lookup(pretrained_checkpoint)

        with EmptyInitOnDevice(
                device=fabric.device, dtype=dtype, quantization_mode=quantize
        ), lora(r=lora_r, alpha=lora_alpha, dropout=lora_dropout, enabled=True):
            model = LLaMA.from_name(name)

            # 1. Load the pretrained weights
            model.load_state_dict(pretrained_checkpoint, strict=False)
            # 2. Load the fine-tuned adapter weights
            model.load_state_dict(adapter_checkpoint, strict=False)

    print(f"Time to load model: {time.time() - t0:.02f} seconds.", file=sys.stderr)

    model.eval()
    model = fabric.setup_module(model)

    tokenizer = Tokenizer(tokenizer_path)
    sample = {"instruction": prompt, "input": input}
    prompt = generate_prompt(sample)
    encoded = tokenizer.encode(prompt, bos=True, eos=False, device=model.device)

    t0 = time.perf_counter()
    output = generate(
        model,
        idx=encoded,
        max_seq_length=max_new_tokens,
        max_new_tokens=max_new_tokens,
        temperature=temperature,
        top_k=top_k,
        eos_id=tokenizer.eos_id
    )
    t = time.perf_counter() - t0

    output = tokenizer.decode(output)
    output = output.split("### Response:")[1].strip()
    print(output)

    print(f"\n\nTime for inference: {t:.02f} sec total, {max_new_tokens / t:.02f} tokens/sec", file=sys.stderr)
    if fabric.device.type == "cuda":
        print(f"Memory used: {torch.cuda.max_memory_reserved() / 1e9:.02f} GB", file=sys.stderr)


if __name__ == "__main__":
    from jsonargparse import CLI

    torch.set_float32_matmul_precision("high")
    warnings.filterwarnings(
        # Triggered internally at ../aten/src/ATen/EmptyTensor.cpp:31
        "ignore", 
        message="ComplexHalf support is experimental and many operators don't support it yet"
    )
    CLI(main)